Pulse amplitude regulation



T. c. HANA 2,509,269

PULSE AMPLITUDE REGULATION May 30, 1950 Filed July 17, 1946 POWER SUPPLY DELAY L] N E KEYING PULSE GENERATOR awe/WM THOMASYC. HANA Patented May 30, 1950 UNITED STATES PATENT OFFICE PULSE AMPLITUDE REGULATION Thomas 0. Hana, Great Neck, N. Y.,.assignor, by mesne assignments, to the United States of America asrepresentcd by the Secretary of the Navy AppIic'ationJ uly 17, 1946, Serial No: 684,381

--scription when taken inconjunction with the ac- -:'companying-drawing in which the single figure thereofrepresents a preferred embodiment of the invention.

-Inaccrdance with the present invention, a pulse modulator circuit is contemplated which will deliver a pulse of constantamplitudeunder yariable conditions involving changes in .pulse repetition 'rate and changes in the available w supply voltageresulting from poor voltage regulation of the power supply. This is accomplished by allowinga delay line which forms-the pulse shape to discharge slowly through a resistance between pulses. Discharge-of-the delay line be- 'tween-pulses-is necessitatedby the factthat the delay line is overcharged immediately after the pulse-period by virtue of its connection in a series resonantcircuitduring the charging period, as hereinafterdescribecl--in'detail. Thus, choice of aiproper-value of resistanceresults in such a discharge of the delay line that, for example, the decrease "in supply Voltage resulting from a heavier load on the power supply when the pulse repetition is increased'i's compensated for by the shorter period of time in which the delay line may discharge.

In the accompanying figure, to which reference is now had, there is shown the proposed pulse modulator circuit comprisinga pair of thyratron ti'ibes ffi and I4 an inductance" I3 and transformer I "whichareconnected in *series between the cathode of the-tube I l and the -plate of the tube In a delay line i2 connected to the junction point 20 of inductance I3 and transformer II; and a resistance i5 in shunt with tube It. The cathode of the tube It is at ground potential and the grid is biased at such a negative voltage by the bias supply I9 and the resistance ii that it is normally at cut-off potential. Since the supply voltage 2| is introduced at the plate of tube 14 and since 12 .a continuous circuit is formed to the plate of tube 1-0 (through resistance I5,inductance I3 and the .primary winding of the transformer II), the .plate of tube is normally at B+ potential.

5 Thus the potential on the high side of the delay .line I2,.which is connected to the common terminal of the inductance I3 and transformer primary winding, is also at B+ potential and the low-side of the delay line is at. ground potential. The re- 10 sistance I8 serves as the-load for the delay line I2 .and has an impedance of such a value that .theprimaryimpedance.of transformerl I is equal to-that ofthe delaylline I2. The delay line 12 .has-an open-circuit impedance at its other end.

For purposes .of explanation, consider that .a keying rpulse is introduced to the gridof the tube -II]. :This pulse maybe formed-in a key-ingpulse CgeneratQriZ, of suchprecision .that pulses accurately spaced in time with respect to .each other will result. If the pulse has sufficient amplitude,

-it-will causethe voltage .on the grid of thetube II] 'to rise above the cut-off. level and the tube I0 will start to cond-uct thus causing/the plate to drop-to a potentialclose to.ground because of thelow i-mpedance'across .the .thyratron tube In which ioccurs during .its conduction .period. The currentthrough the tube In results from the dis- -chargeof the delay line I2. and this discharge .passes throughthe-primary windingof the trans- 930 former I-I, inducing .a voltage which appears across the load-IB. The voltage at the terminal 2-0, which connects thehigh side of the delay .line !2 to the junction-point of the inductance I3 and the primary-winding of the' transformer H,

'35 then'dropsto half of the voltage towhich the line was charged since the primary impedance of transformer II is'equ'al to the delayline impedance.

Atterthedelay line I2 has exhausted its charge -40 through-the tube I'll, the latter may not imme- "diatelystopconducting because of the large numaberzof'ions still presentin the tube. Since a voltagediiference' exists 'allalong the path comprising the ;.power supply -:2 I, resistance I5, induct- =ance I 3,:transformer'I I, tube I0 and through the appear across the load I8.

that the value of the resistance I5 will predomimate and thus most of the voltage will appear across this resistance, thus causing the voltage at the cathode of the tube 14 to be fairly close to ground. As has been stated above, the resistance values of the inductance I3 and transformer II are low as compared to the value of the resistance l5 and thus the voltage difference existing between the cathode of the tube [4 and the plate of the tube I will be relatively low. Thus the potential at the anode of tube It! remains low after the line is discharged and the tube will quench;

After tube 1 0 stops conducting its anode will not immediately rise to B-]- potential because terminal 20 can rise only as the delay line is charged through resistance IS. The plate of the tube [0 is connected to the grid of the tube It, and the voltage difference, which now exists between grid and cathode of the tube I4, will be low enough to excite the tube l4 after tube It! has quenched. The subsequent change in potential at the anode of tube ID will not return it to a conducting state bec'ause of bias supply 19 connected to its grid. Once the tube 14 becomes excited, it presents a very low impedance. Additionally, the reactance of the inductance is chosen so that at some sufliciently high frequency it is in series resonance with the capacitive reactance presented by the delay line 12. Thus, a very low resultant impedance is presented by the circuit comprising the power supply 2!, the tube M, the inductance l3 and the delay line l2, and a high surge current results. This current drives the voltage at the terminal 2!! to a maximum of twice the B+ voltage and cuts 01f the tube I4 since the cathode voltage is now higher than the plate voltage. As a result of the fact that the delay line potential is now higher than the potential of the power supply itself, the delay line is able to discharge slowly through a circuit comprising the inductance l3, the resistance l5 and the power supply, with the rate of discharge depending mainly upon the value of the resistance l5. If the resistance I5 is chosen to be very large, negligible discharge will take place in the delay line l2 before the arrival of the next pulse at the grid of tube l0 fires the tube and discharges the line. If the resistance I5 is made to have some smaller value, however, the delay line potential is able to decrease somewhat before the next pulse. Assume now that the pulse repetition rate is increased. Because of the increased load on the .power supply and the poor voltage regulation that may exist in the power supply, the available B+ voltage will decrease. This decrease in the available B-|- voltage will in turn cause the overshoot of voltage at the terminal 20, which occurs from the conduction of the tube l4 after the delay line l2 has discharged, to be less than usual, since the amount of overshoot is proportional to the B+ voltage available. This decrease in the overshoot voltage is compensated for, however, by the fact that the delay line potential is not able to decrease as much with higher repetition rates from discharge through the power supply as would occur with lower repetition rates, the reason for this being that the time interval between pulses is less for higher repetition rates. It may thus be seen that by inserting a fairly low value for the resistance IS, a pulse may be formed whose amplitude will be substantially constant regardless of the pulse repetition rate or the quality of voltage regulation in the power supply.

While a certain preferred embodiment of this invention has been described, it is realized that many modifications and variations of this invention may be made and no limitations upon this invention are intended other than may be imposed by the scope of the appended claims.

What is claimed is:

1. A pulse generator for producing variable frequency pulses having substantially constant amplitude from a power supply having poor voltage regulation, said pulse generator comprising a transmission line section, a resonant charging path including a first switch tube for charging said line from said power supply to substantially twice the power supply voltage, a discharge path for said line including an output transformer and a second switch tube, pulse frequency control means operative to repetitively excite said second switch tube at the desired output pulse frequency, coupling means coupling said second switch tube to said first switch tube operative to excite said first tube at the conclusion of each line discharge through said second tube, and resistance means shunting said first switch tube operative to discharge said line towards the voltage of the power supply during the interval between the charging of said line and the next successive discharging thereof.

2. A pulse generator for producing variable frequency pulses having substantially constant amplitude from a power supply having poor voltage regulation, said pulse generator comprising a transmission line section, a series resonant charging path for charging said line from said power supply to substantially twice the power supply voltage, said charging path including a first switch tube and an inductance in series, the inductance being at the line end Of said series path, a discharge path for said line including an output transformer and a second switch tube, pulse frequency control means operative to repetitively excite said second switch tube at the desired output pulse frequency, coupling means coupling said second switch tube to said first switch tube operative to excite said first tube at the conclusion of each line discharge through said second tube, and resistance means shunting said first switch tube and cooperatively associated with said inductance to discharge said line towards the voltage of said power supply during the interval between the charging of said line and the next successive discharging thereof.

THOMAS C. HANA.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,405,070 Tonks July 30, 1946 2,409,897 Rado Oct. 22, 1946 2,416,114 Nelson Feb. 18, 1947 

